Gradient Ammonia Storage SCR Catalyst for Cold-Start NOx Reduction
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Solution Overview
Problem
SCR catalytic converters face inefficiencies in nitrogen oxide reduction across a wide temperature range, particularly in cold conditions, leading to nitrogen oxide breakthroughs and exceeding of NOx limit values in vehicle cycles.
Innovation Solution
An SCR catalytic converter design with ammonia storage materials distributed along the catalyst carrier in a gradient fashion, where areas with lower ammonia storage capacity precede those with higher capacity, utilizing zeolites and zeolite-like materials for catalytic activity, and maintaining even distribution of catalytically active material without increase on particulate filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ammonia storage materials are uniformly distributed on the catalyst carrier, then the catalytic activity is maintained, but the nitrogen oxide reduction efficiency is insufficient in cold conditions
Solution Approach 1:
The patent applies local quality by creating a gradient distribution of ammonia storage materials on the catalyst carrier. The inlet area has lower ammonia storage capacity while the outlet area has higher capacity. This non-uniform distribution optimizes the SCR reaction efficiency across different temperature conditions, particularly improving cold-start performance without sacrificing overall catalytic activity.
2Temperature
If the SCR system is used in cold temperature ranges, then ammonia storage is required, but urea deposits and reaction products accumulate causing system failure
Solution Approach 1:
The patent changes the physical-chemical parameters of the catalyst system by implementing a gradient distribution of ammonia storage materials. This parameter change allows the system to operate reliably in cold temperature ranges (below 200°C) by optimizing ammonia availability, preventing urea deposit accumulation, and maintaining high nitrogen oxide conversion efficiency without compromising system reliability.
3Productivity
If ammonia storage capacity is increased throughout the catalyst, then cold-start performance improves, but the cost and complexity increase
Solution Approach 1:
The patent resolves this contradiction by applying local quality through a gradient distribution strategy. Instead of uniformly increasing ammonia storage capacity throughout the entire catalyst (which would increase cost and complexity), the invention concentrates higher ammonia storage capacity specifically in the outlet area where it is most needed for cold-start performance, while maintaining lower capacity in the inlet area. This localized optimization achieves improved cold-start conversion without proportionally increasing overall system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances nitrogen oxide reduction efficiency across varying temperatures, reduces ammonia slip, and minimizes costs while maintaining activity, achieving higher effectiveness or cost savings compared to prior art.
Implementation Method 1
a SCR catalytic converter having one or more storage materials for ammonia (NH3)
Implementation Method 2
materials with ammonia storage capacity are distributed on the supporting body/bodies
Implementation Method 3
The material determining the catalytic activity for the reaction considered is made of a material which has ammonia storage capacity
Implementation Method 4
as the latter compounds selected from the group comprising zeolites, such as mordenite (MOR), Y-zeolite (FAU), ZSM-5 (MFI), ferrierite (FER), chabazite (CHA), and β-zeolite (BEA) as well as zeolite-like materials
Data Source
AI summary
The invention relates to the possibility of improving selective catalytic reduction (SCR), which is the selective reaction of nitrogen oxides with ammonia in the exhaust gas of combustion processes on an exhaust-gas catalytic converter suitable therefor—the SCR catalytic converter. For this purpose, materials used in the catalytic converter for storing ammonia are distributed on the catalyst carrier in such a way that, viewed in the flow direction, a region having low ammonia storage capacity is followed by a region of higher ammonia storage capacity.